Utilizing biomimetic oligopeptides to probe fibronectin-integrin binding and signaling in regulating macrophage function in vitro and in vivo

Biomimetic oligopeptides were employed to elucidate the molecular mechanism s of fibronectin-integrin interaction in regulating macrophage function. Ol igopeptides were designed based on of the functional structure of fibronect in and grafted onto a polymer network containing polyethyleneglycols. Macro phage adhesion was independent of the peptide identity that contained seque nce RGD, PHSRN, PRRARV, or combinations thereof in an integrin-dependent fa shion in vitro. However, integrin-dependent foreign body giant cell (FBGC) formation in vitro was highly dependent on both RGD and PHSRN in a single p eptide formulation and with a specific orientation. In vivo results showed that peptide identity played a minimal role in modulating the host inflamma tory response and adherent macrophage density. RGD-containing peptides medi ated a rapid FBGC formation by 4 days of implantation by significantly incr easing both the number of macrophages that participate in the cell fusion p rocess and the rate of cell fusion. Both RGD and PHSRN domains were importa nt in mediating FBGC formation at later implantation periods. In vitro intr acellular signaling studies revealed that the requirement of protein tyrosi ne kinase and serine/threonine kinase activation and cross-talk compensatio n for macrophage adhesion dynamically varied with surfaces and culture time . Protein kinase C-dependent adhesion was related to RGD and PHSRN sequence s, and to the sequence orientation thereof in a form of GGGRGDGGGGGGPHSRNG. Furthermore, we observed a multiple effect of the mitogen-activated protei n kinase/extracellular-signal-regulated kinase signaling factor in mediatin g macrophage adhesion, which depended on the method of ligand immobilizatio n. These findings represent a mechanistic correlation between the role of s ubstrates and protein functional architectures in ligand-receptor recogniti on and post-ligation signaling events that control cellular behavior in vit ro and in vivo.